The River Cottage Meat Book by Hugh Fearnley-Whittingstall 544pp, Hodder & Stoughton, £25

When Jane Grigson wrote her definitive work on pork in 1967 and assumed the mantle of scholar cook from Elizabeth David, it was French cuisine she wanted to instruct us in. Just as much of David's passion about food was dedicated to expanding British horizons by looking abroad, so Grigson took her readers on a tour of provincial France and the guts of its charcuterie.

Hugh Fearnley-Whittingstall's latest book, a vast tome with the word MEAT embossed defiantly in large, blood-red letters across its cover, marks him out as worthy successor to that tradition of learned chef. These days, of course, it is not so much foreign gastronomy that is a mystery as what goes on with food produced under our very noses. Fearnley-Whittingstall takes the bull by the horns - often quite literally, since he farms his own meat - and launches a passionate defence of the carnivore's position. He follows with a devastating critique of modern factory farming and British supermarket practice. His polemic is reminiscent of David's introduction to her English Bread and Yeast Cookery in 1977, which documented the ills of factory bread. Like its predecessor, Fearnley-Whittingstall's attack is carefully researched, revelatory and powerful.

The apologia for meat is something new in a book intended for the kitchen shelf - a recognition that in today's world, where one half of the world starves while the other half suffers from the diseases of excess, eating is not only a political but a moral act. You can either duck the issues around feeding animals large quantities of grain that could be used more efficiently to feed humans, and then killing them, or you can confront them. Having done the latter, Fearnley-Whittingstall wants you to enjoy your food all the more.

While admitting to great respect for vegetarians, particularly those who refuse to eat meat as a stand against the routine cruelty and suffering we impose on our livestock, he argues against the vegetarian position. Historically, man has evolved eating meat as part of a mixed diet, but he acknowledges that is not enough of a defence today. In societies where food is plentiful, we no longer need to eat meat for health, and in a post-Darwinian world where our biological links to the rest of the animal kingdom are clear, animals undoubtedly come within our moral sphere. However, he argues, any species pursuing its interests has an impact on the rest of the planet's life. Humans inevitably affect animals and vegetarians are no different. They upset the balance of nature too.

A mixed agricultural economy that uses meat thriftily and integrates arable and livestock farming - with the animals' manure feeding the soil so that the crops will grow to feed the animals in turn - is efficient, sustainable and protective of the landscape. Moreover, the dependency of domesticated meat species on us would not end just because we stopped killing them. They would not revert to the wild; we would still have to be responsible for their welfare and demise. We could hardly abandon them to "tamelife parks", as he puts it.

But our moral authority to kill animals for food can only be based on our offering them a better deal in life than they would get without our help. The prevailing system of intensive livestock farming is a complete abrogation of that responsibility. It is systematically abusive. Pain is routine, stress almost constant, disease widespread. We should raise and kill animals without cruelty and then do them the respect of eating every last bit of them, from crisp griddled pigs' ears to slow-braised oxtails.

There will be those who disagree with him, and some, like Matthew Scully in Dominion (2003), who argue the opposite in greater depth, but Fearnley-Whittingstall is persuasive and direct. His plea not to shirk "the moral dimension in your dealings with meat" is followed, logically and honestly, by full colour pictures of his calves being slaughtered, though, without the noise and smell, the glossiness of the images fails to convey the messiness of it all.

The killing out of the way, he moves on to expose real horrors - factory production that leads chickens to suicidal rushes that suffocate thousands of birds, intelligent pigs reduced to stress-induced chewing of each other's tails, the use of antibiotics, the adulteration.

Some of this will be familiar territory to Guardian readers, but there is plenty that's new. He explains how much beef today comes not from beef cattle bred to fatten beautifully but from dairy-cross cows, which have distinctly bony behinds and are the byproduct of the calving needed to keep dairy cows in milk year on year. We find out why supermarkets prefer to bypass the hanging period that traditionally makes meat tasty and tender - meat loses moisture as it hangs, which paradoxically keeps it more moist when it cooks because the water in wet, under-hung meat expands during cooking, stretches the fibres of the meat and leaches out, leaving it dry and tough. But hanging means weight loss and reduced profits, so factories don't like it. We also learn why vacuum packing gives meat a nasty metallic tang - it cannot breathe but ends up marinading in oxidised blood.

The technical bits of the book are especially good and equip you with an understanding that is all too often absent from celebrity chef offerings. Detailed explanations of the main cuts of each animal are accompanied by full-colour pictures, and the sort of opinionated explanation that tells you just what you need to know.

We learn that silverside is the classic cut from the back of the thigh, from the muscles that do all the hard work propelling their owner from one place to another (ie, quite tough). In some butchers, it is tied up and sold as a cheap roasting joint, but conventional fast roasting it is "a complete waste of time". Topside is from the inner thigh; cut as a roasting joint it will be too tough, unless roasted slowly with a little water in the tin. Sirloin, from the lower middle back, on the other hand, is one of the finest joints for fast roasting. Do not salt too soon - it only draws out the juices. Marinate sparingly, as it has the same effect as the vacuum pack above.

Scholar cook he may be but we are still in celebrity chef territory, so Fearnley-Whittingstall wears his learning with much more personality than David or Grigson would ever have allowed themselves. We see him humping carcasses around in his crumpled T-shirts, we hear him shudder at the thought of being dependent on supermarket meat, we watch his wild head of hair bent over a whole pig he is preparing for spit roasting. For most of us this is the stuff of fantasy, but none the less infectious for that, particularly as it is delivered with lively writing and endearingly corny puns.

The recipe section is not comprehensive but most of the classics are here and well presented, from the incredibly cheap but labour-intensive breast of lamb Sainte Menehould to the incredibly expensive and labour-intensive roast rib of beef with Yorkshire pudding. You can learn what to do with pigs' trotters and how to make your own bacon. Favourites are also revisited - you'll find an excellent bolognese (despite the index's best efforts to hide it), hamburgers, glazed spare ribs and jerk chicken.

My only cavil is that the book is too heavy. It's a work you want to absorb and savour as well as prop open on the kitchen counter, but the sheer weight of its glossy paper and pictures needs a farm labourer's muscles to lift.

· Felicity Lawrence's book on the politics of food, Not on the Label, has just been published by Penguin